Ceraunias, or Ceraunius, Lapin, in natural history, a fort of flinty stone of no certain colour, but of a pyramidal or wedge-like figure; popularly supposed to fall from the clouds in the time of thunder-storms, and to be possessed of divers notable virtues, as promoting sleep, preserving from lightning, &c. The word is from the Greek θύρανος, thunderbolt. The ceraunia is the same with what is otherwise called the thunder-stone, or thunder-bolt; and also sometimes sagitta, or arrow's-head, on account of its shape. The ceraunia are frequently confounded with the ombrice and brontia, as being all supposed to have the same origin. The generality of naturalists take the ceraunia for a native stone, formed among the Pyrites, of a saline, concrete, mineral juice. Mercatus and Dr Woodward assert it to be artificial, and to have been fashioned thus by tools. The ceraunia, according to these authors, are the heads of the ancient weapons of war, in use before the invention of iron; which, upon the introduction of that metal, growing into disuse, were dispersed in the fields through this and that neighbouring country. Some of them had possibly served in the early ages for axes, others for wedges, others for chisels; but the greater part for arrow-heads, darts, and lances. The ceraunia is also held by Pliny for a white or crystal-colored gem, that attracted lightning to itself. What this was, is hard to say. Prudentius also speaks of a yellow ceraunia; by which he is supposed to mean the carbuncle or pyropus.